Click mechanism for precise control of a tuner



June 8, 194s. C. L. RICHARDS 2,442,935

CLICK MECHANISM FOR PRECISE CONTROL oF A TUNER Filed Dec., 22, 1944 a@/5 n @Pm INVENTOR ATTORNEY Patented June 8, 1948 CLICK MECHANISMFORPRECISE CONTROL F A TUNER Claude Langdon Richards, London, England, as-

signer to The Hartford Nationalv Bank & Trust Company, Hartford, Conn.astrustee Application December 22, 1944, Serial No. 569,405 In GreatBritain October 18, 1943 Section 1, Bublic Law 690, August 8, 1946Patent expires October 18, 1963 (Cl. Z50-40) Claims. 1

In tuning arrangements for wireless-receivers and like apparatus inwhich it is desired to tune electrical circuits to predeterminedfrequencies, it is known to provide a so-called click mechanism wherebythe tuning member is located in a predetermined setting by theengagement of a pin or arm in a recess, a spring being usu-ally providedwhich tends to cause the, pin or arm to be at the bottom of the recess.The difculty arises that for ease in manipulation, particularly inmoving from one tuning position to another, each recess must have gentlysloping sides, whereas for precise location of the tuning member steepsides to the lrecess are necessary.

The object of the present invention is to provide a click mechanismwhich enables both ease in manipulation and precision of location.According to the presentl invention at least one of the click elementsis resiliently mounted' and is adapted to be urged electromagneticallyout of its rest position into a position giving a greater degree ofengagement with the other. Release for easy manipulation can then beobtained by deenergising the electro-magnet.

In one form of the present invention the tuning member to be located,consisting` for example of the rotatable shaft and moving vanes of avariable condenser, carries a disc at right angles to the shaft andmounted on the disc are arms adapted to engage in a recess between thepole- 30 `pieces of an electromagnet mounted for pivotation about a xedaxis and springloaded so as to assume a predetermined rest position whennot energised.

In order that the invention may be more readily understood, referencewill now be had to the accompanying schematic drawings in which:

Fig. 1 shows the general disposition of the click mechanism in relationto the other parts of the tuning arrangement,

Fig. 2 shows a preferred form of clickV mechanism according to theinvention,

Fig. 3 is an explanatory diagram.

In Fig. .1., the wireless receiver is assumed to be of the kind in whichtuning is effected by means of a variable condenser controlled by arotary shaft. It will however be apparent that the click mechanism ofthe present invention is applicable to all tuning arrangements in whichaxis irrespective of the nature of the circuit component which isthereby adjusted.

From the tuning knob l, a cord drive 2 is taken. to a drum 3 which issecured on the shaft 5 of the variable condenser 6 (not shown indetail). After passing round the drum 3 t-he cord 2' is taken to a guidepulley 4 before returning to the tuning knob. In this Way it is possiblefor the cord 2 to be led on and oil' the drum 3 at the same point, therun of -cord between tuning knob and drum 3 being at 180 to the run ofcord between drum 3 and pulley 4, and Iboth runs of cord lying in thetangent plane at the point where the cord is led on and oi. Also securedto the shaft 5 is a disc 8 carrying a number of click arms il; These areadapted to co-operate in a predetermined position with a click recessI0, which will be described more fully hereinafter with reference toFigs. 2 and 3.

To show the setting of the tuning condenser 6 a scale l2 is provided,over which an indicator Il is caused to travel by a cord drive I3. Thecord passes round guide gulleys I4 and is led on and oil the drum 3 atthe same point in opposite tangential directions, simil-arly to the cord2. With this arrangement, the drive and indicator cords constitute abalanced load on the spindle 5.

The condenser 6 and the click mechanism are mounted on a common rigidbase 1 which preferably also carries a bracket l5 supporting t-hepulleys- 4 and I4.

Reference will now be had to Fig. 2, which shows only part of the disc 8mounted on the spindle 5. The arm S is provided with a stepped tang 2liwhereby it is pivotally mounted in a substantially triangular aperture2l in the disc 8; The arm 5) can be secured in the precise angularsetting in relation to the spindle 5 by means of the clamping devicecomprising the bolt 23 and washer 24, the bolt 23 passing through anarcuate slot 22 concentric with the centre of pivotation of the arm Si.The projecting end` of the arm 9 is shaped as a rounded head for smoothengagement in the click recess.

The click recess is formed between twov cheeks 25 constituting thepole-pieces of an electromagnet. These cheeks 25 are integralA with orsecured to the cores of magnetising coils 26, the magnetic circuit beingcompleted through tuning is effected by turning a shaft about its a yokemember 3l whereby the electromagnet as a whole is mounted for pivotationso that the pole-pieces move towards and away from the spindle 5.Adjacent the pole-pieces 25 a nonmagnetio strip 21 is clamped to thecore of the electromagnet so as to maintain the pole-pieces at apredetermined spacing. The clamping strip 21 projects below theelectromagnet and is engaged by opposed coil springs 28 which tend tooppose displacement of the strip 21 fromits mean or rest position. Thesprings 28 are supported by a rod 29 which passes through an aperture inthe end of the strip 21 and is carried by a U-shaped bracket member 30which in turn is rigidly mounted in relation to the base plate 1 (Fig.1). The pivotal mounting of the yoke 3| en which the electromagnet iscarried is effected by two ball bearings 32 vwhich are carried by amassive frame 33 which is rigidly secured in relation to the base platev1 (Fig.,1).

As best seen from Fig. 3, the arrangement is` such that when theelectromagnet is not energised the end of the arm 9 when'in ,the lclickposition is only in slight engagement with the cheeks 25 defining theclick recess IIJ. cheeks 25 are so shaped as to present a gentleinclination to the end of the arm 9 so that the latter can readily causethe electro-magnet system to pivot away from the spindle 5 to enable thearm S to enter the recess I0. The depth of engagement is indicated bythe zone a-b and within this Zone the inner faces of the cheeks 25 aresmoothly rounded so that the arm 9 can be caused to disengage byrotation of the tuning knob (knob I', Fig. l). Beyond the zone a--b therecess I0 has steep sides tending towards parallelism. When theelectromagnet is energised, the gentle inclination of the outer faces ofthe cheeks 25 still enables the arm 9 to cause the pivotal movement ofthe electromagnet 2S necessary to permit the arm 9 to enter the recessIU, but when engagement occurs it is much deeper due to the magneticattraction between the energised pole-pieces 25 and the arm 9, which ismade of magnetic material of low retentivity. Due to this deeperengagement there is contact between the arm 9 and both sides of therecess IIJ, whereby the arm 9 is precisely located and with it thespindle 5. To release the arm 9 for a fresh tuning operation theelectromagnet is de-energised and is thereupon restored by the springs28 to the position in which the depth of engagement corresponds to thezone aP-b and the arm 9 can be disengaged by operating the tuning knob.The Zone a-b can be made of any desired depth and may even vanish, inwhich case there is no engagement at all in the absence of energisation.

To set the arm 9 in the precise angular position to give the desiredtuning adjustment, it is brought into engagement with the click recessI0 with the electromagnet 26 energsed. Then with the clamping bolt 23released, the spindle 5 is brought into the desired position, whereafterthe arm 9 is again clamped to disc 8. In this way mechanical strains onthe condenser during the operation of adjustment are largely eliminated.

The control of the circuit for the electromagnet 26 can be of anyconvenient form. A suitable arrangement is that indicated in Fig. 1,where the circuit I6 includes a battery I1 and switches I8 and 35. Thebattery I1 could be replaced by any other convenient source ofenergising current. The switch I8 is coupled by a link Ill to the tuningknob I so that the switch I8 can be opened and closed as required duringtuning. A

central push button on the tuning knob could for example be provided forcontrolling the switch I8. Switch 35 is coupled by a link 36 with theband selector switch 34 so that the click tuning operates only on thedesired tuning bands.

It will be apparent that the click mechanism according to the presentinvention gives rise to a minimum of mechanical wear on the click pinand the cheeks of the click recess while enabling a maximum of precisionof location to be achieved; a repeat accuracy of frequency of the orderof 5 parts in l100,000 is readily obtained. If desired, a smallpermanent magnet can be mounted at the v, back of the pole-piece gap tocollect any iron dust formed by wear, but owing to the slight wearinvolved this `precaution will in general be unneci l essary.

The f I claim:

. 1. Tuning apparatus for wireless receivers and thevlike comprising aclick-mechanism for said tuning apparatus including a click-pin, meansproviding a click-recess, control means for causing the said click-pinto move into and out of engagement relative to the said recess andelectromagnetic means for varying the degree of said engagement.

2. A tuning control apparatus as set forth in claim 1 in which the saidclick-recess means is mounted for pivotation about a fixed axis andspring loaded so as to assume a predetermined rest position.

3. A tuning control mechanism as set forth in claim 1 in which theclick-pin is made of magnetic material and its attractive force causes arelative `movement between the said click-pin and said click-recessmeans so that the click-pin moves to a position of greater engagement inthe said click-recess.

4. A tuning mechanism as set forth in claim 1 in which there is a slightengagement between the said click-pin and the said click-recess meanswhile the said electromagnetic means is nonenergized.

5. Tuning apparatus for wireless receivers and the like comprising aclick-mechanism for said tuning apparatus including a plurality ofclickpins, means providing a click-recess, control means for causing thesaid click-pins to move into and out of engagement relative to the saidrecess and electromagnetic meansl for moving the said recess into aposition of greater degree of engagement with the said click-pins whenenergized.

6. Click-mechanism as set forth in claim 5 in which each of the saidclick-pins is adjustably secured to the said control means.

7. Tuning apparatus for wireless receivers and the like comprising aclick-mechanism for said tuning apparatus including a plurality ofclickpins, means provid-ing a click-recess, control means for causingthe said click-pins to move into and out of engagement relative to thesaid recess, electromagnetic means for moving the said recess to aposition of greater engagement with the said pins and means for driveconnecting the said clickpin control mean-s to the tuning control of thesaid receiver.

8. A tuning mechanism as set forth in claim 7 in which additional drivemeans is taken from the click-pin control means to a tuning indicator ofthe said receiver.

9.A tuning mechanism as set forth in claim 1 in which a switchcontrolling the said electromagnetic means is operatively associatedwith a tuning knob of the said receiver to permit the saidelectromagnetic means to be de-energized before 6 changing the tuningstatus of the said receiver.

10. Tuning apparatus for wireless receivers and 1 REFERENCES CITED thelike comprising a, click-mechanism for said The following references areof record in the tuning apparatus including a plurality of clickle 0fGhS Patent: pins, means providing a click-.recess control 5 UNITEDSTATES PATENTS means for causing the sald chck-pms to move mto and outof engagement relative to the said recess, Number .Name Dateelectromagnetic means for moving the said recess 2025213 Relnken DEC-24, 1935 to a position of greater engagement with the said 2,030,129Wheller Feb. 11, 1936 pins, and a band selector switch for de-energiz-10 2,031,636 ThPmaS May 25, 1937 ing the said electromagnetic means atselected 2,190,332 ElllOtt Feb. 20, 1940 positions of the said selectorswitch. 2,205,170 JOhnSOn June 18, 1940 2,275,284 Carlson Mar. 3, 1942CLAUDE LANGDON RICHARDS. 2,312,035 Groenenberg et al. Feb. 23, 1943

